Pedestrian Navigation Sensor Fusion for Indoor Drift Correction
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Solution Overview
Problem
Conventional pedestrian navigation systems face limitations, such as satellite-based systems being ineffective in heavily forested areas or indoors, and inertial navigation systems experiencing drift issues over time, leading to inaccurate tracking.
Innovation Solution
A hybrid navigation system combining a GPS receiver with inertial instruments, including accelerometers and gyroscopes, and a magnetic compass, which calibrates using GPS signals when available and relies on inertial and magnetic instruments during outages, with additional features like ultrasonic distance measurement between feet to enhance accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If satellite-based navigation systems are used, then positioning accuracy is improved, but the system becomes ineffective in heavily forested areas or indoors
Solution Approach 1:
The patent combines multiple navigation systems (satellite-based GPS and inertial navigation systems with accelerometers and gyroscopes) into a hybrid system. The inertial measurement unit (IMU) provides positioning data through dead reckoning calculations, complementing satellite signals to maintain accuracy in environments where GPS is unavailable such as forests and indoors.
Solution Approach 2:
The patent introduces an intermediary processing system that receives signals from both satellite-based and inertial navigation systems, then integrates these signals through signal processing to generate unified positioning information. This intermediary layer reconciles the different measurement approaches and provides continuous accurate positioning regardless of environmental conditions.
2Adaptability or versatility
If inertial navigation systems are used, then the system works indoors and in forests, but positioning accuracy deteriorates due to drift over time
Solution Approach 1:
The patent implements feedback mechanisms where the inertial navigation system's output is continuously monitored and corrected using available satellite-based positioning data. When satellite signals are available, they serve as reference points to correct drift accumulation in the inertial system. The system also uses magnetic compass data to correct heading deviations, creating multiple feedback loops that maintain accuracy.
Solution Approach 2:
The patent performs preliminary calibration of the inertial measurement unit by determining its orientation relative to magnetic north using the magnetic compass before navigation begins. This preliminary alignment establishes an accurate reference frame that reduces initial drift errors. The system also pre-processes accelerometer and gyroscope data to establish baseline characteristics that minimize measurement drift during operation.
3Ease of operation
If magnetic compass is used, then heading determination is provided, but the compass may be affected by magnetic interference from the pedestrian's body or environment
Solution Approach 1:
The patent segments the magnetic measurement function by separating the magnetic compass from the inertial measurement unit and positioning system. The magnetic compass is positioned to measure ambient magnetic field direction independently, while the IMU handles acceleration and rotation measurements. This segmentation allows the magnetic field measurements to be processed separately and combined with other navigation data, reducing the impact of magnetic interference from the pedestrian's body or environment on the overall navigation accuracy.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The hybrid system provides robust and accurate tracking of pedestrian movement, maintaining precision even during GPS outages by calibrating inertial instruments with magnetic data and using sensor fusion to reduce drift, thereby improving navigation in diverse environments.
Implementation Method 1
inertial instruments, including accelerometers and gyroscopes
Implementation Method 2
inertial instruments, including accelerometers and gyroscopes
Implementation Method 3
measuring an ambient magnetic field with the magnetic instrument
Implementation Method 4
Detecting the stride length includes emitting a sonic pulse at one foot of the pedestrian, and receiving the sonic pulse at another foot of the pedestrian
Implementation Method 5
receiving positioning signals at the pedestrian; The positioning signals include global navigation satellite system signals
Data Source
AI summary
Among other things, positioning a magnetic instrument on a pedestrian; positioning an inertial instrument on a foot of a pedestrian; receiving positioning signals at the pedestrian; aligning the inertial instrument based in part on the received positioning signals; calibrating the magnetic instrument using the inertial instrument; and tracking the pedestrian using the calibrated magnetic instrument and the inertial instrument.